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Molecular determinant for run‐down of L‐type Ca 2+ channels localized in the carboxyl terminus of the α 1C subunit
Author(s) -
Kepplinger Klaus J. F.,
Förstner Günter,
Kahr Heike,
Leitner Katharina,
Pammer Patrick,
Groschner Klaus,
Soldatov Nikolai M.,
Romanin Christoph
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00119.x
Subject(s) - chemistry , protein subunit , channel blocker , amino acid , niflumic acid , peptide sequence , stereochemistry , biochemistry , microbiology and biotechnology , biology , organic chemistry , gene , calcium
1 The role of the sequence 1572‐1651 in the C‐terminal tail of the α 1C subunit in run‐down of Ca 2+ channels was studied by comparing functional properties of the conventional α 1C,77 channel with those of three isoforms carrying alterations in this motif. 2 The pore‐forming α 1C subunits were co‐expressed with α 2 δ and β 2a subunits in HEK‐tsA201 cells, a subclone of the human embryonic kidney cell line, and studied by whole‐cell and single‐channel patch‐clamp techniques. 3 Replacement of amino acids 1572‐1651 in α 1C,77 with 81 different amino acids leading to α 1C,86 significantly altered run‐down behaviour. Run‐down of Ba 2+ currents was rapid with α 1C,77 channels, but was slow with α 1C,86 . 4 Transfer of the α 1C,86 segments L (amino acids 1572‐1598) or K (amino acids 1595‐1652) into the α 1C,77 channel yielded α 1C,77L and α 1C,77K channels, respectively, the run‐down of which resembled more that of α 1C,77 . These results demonstrate that a large stretch of sequence between residues 1572 and 1652 of α 1C,86 renders Ca 2+ channels markedly resistant to run‐down. 5 The protease inhibitor calpastatin added together with ATP was able to reverse the run‐down of α 1C,77 channels. Calpastatin expression was demonstrated in the HEK‐tsA cells by Western blot analysis. 6 These results indicate a significant role of the C‐terminal sequence 1572‐1651 of the α 1C subunit in run‐down of L‐type Ca 2+ channels and suggest this sequence as a target site for a modulatory effect by endogenous calpastatin.